Characterization and serotype distribution of Aggregatibacter actinomycetemcomitans detected in a population of periodontitis patients in Spain.

Objective: To investigate the serotype distribution of Aggregatibacter actinomycetemcomitans (A. a.) and the polymorphism of the genes that codify the leukotoxin (ltx) and the operon of the cytolethal distending toxin (cdt) in periodontitis patients in Spain. Materials and methods: Forty A. a.-positive periodontitis patients were included in the study (mean age 45±7.8 years, 62.5 % female) and their clinical periodontal status was assessed. On average, 1 to 2 isolates from each patient were subcultured and characterized by specific PCR reactions. Results: Serotype distribution analysis concludes that the most frequent serotype was a and that 29 patients showed monoinfection. The 11 patients that showed coinfection were infected mostly with serotypes a and b. From these 40 isolates 15 corresponded to serotype a, 8 to serotype b and 6 to serotype c. Monoinfection with serotypes d, e or f was not found. Further characterization of these samples with leukotoxin specific PCR reaction showed that none of the 40 samples presented the 530-bp deletion called ?530 in the leukotoxin's promoter region, which characterizes the JP2 strain. As for the Cdt, the operon that codifies for the toxin was present in 85 % of the samples. Conclusions: The most common serotypes were a and b. Serotype a was the most frequent in monoinfections, while serotypes d, e and f were not detected. In the majority of samples, operon that codifies the cdt (85%) and the genes responsible for the codification of leukotoxin (100%) were found. None of the isolates belonged to the JP2 strain.